Measured-service telephone system



). M. TAGGART ET AL.

MEASURED SERVICE TLPHONE SYSTEM Oca. 28 '1924,

Oct. 28. n924. Lsssi D. M. TAGGART ET AL MEASURED SERVICE TELEPHONE SYSTEM- vFiled nec. 15, 1920 s sheets-sheets Oct. 28 `1 924. ,51335-1 D. M. TAGGART ET AL MEASURED SERVICE TELEPHONE sYsTEm Fiied Dec. 16,

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0.1M. TAGGART ET AL MEASURED SERVICE TELEPHONE SYSTEM Filed Dec.. 16 1,920

5 Sheets-Sheet 5 Paienied oci. 2e, 1924. l i 1,513,351-

DAWSON M. TAGGART, OF LANCASTER, PENNSYLVANIA, AND FREDERICK J. SCUDDER,

F LONG ISLAND CITY, NEW YORK, ASSIGNORS TO 'WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION 0F NEV YORK.`

IVIliASl'JlEtlI)-STLERVIIICIE.4 TELEPHONE SYSTEM.

Application filed December 16, 1920. Serial No. 431,14L

To all whom t may concern: cessful establishment of a connection, and

Be it known that we, DAwsoN M. TAGGART which becomes eiiective to establish an op- 55 and FREDERICK J. SGUDDER, citizens of the erating circuit for the callingv subscribers United States, residing at Lancaster, in the message register upon the release of the 5 county of Lancaster, State of Pennsylvania, established connection. The subscribers and Long Island City, in the county "of message register is associated with the in- Queens, State oit New York,frespectively, comingy terminals of ythe subscribers line 60 have invented certain new and useful Iniand is operated over a circuit extending provements in Measured-Seiw'ice Telephone through awiper 'and bank Contact of his' Systems, of which the following is a full, individual line switch.. f f

clear, concise, and exact description. l When,'however, it is desired to vequip cer-y This invention relates to a telephone sys-y tain lines terminatingin van ofce. with two 65 tem in which connections are established substatons for supplyingtwo partyv line betweensubscribers lines by means of me- Service, it is then necessary t0 Vassociate two chanical switching devices, and more parmessage registers with the incoming terticularly to a system in which -successive minals of each of such lines and-to provide calls are registered upon message registers discriminating means at thedstrot S9160-y 70 individual to subscribers lines. tor 'for' operating only the register of the In telephone systems of this character concalling` party. The discrimination is.` atnections between subscribers lines are estained by providing a special testcondition tablislied by means of mechanical switching upon the party line which is placed thereon devices, which are controlled in their seleconly When 0H@ Of the 'tWO Parties. hS inititive movements by impulse sending mechaated the call. t c

nisin under the control ofthe subscribers at The special discriminatory test condition,

U their respective substations. `Following the according to thisinventionis obtained by extension of a connection to a desired subplacing a ground on vthe tip conductor of the scribers line, it' the connection is successline through the call-bell at the substation S0 fully established and the desired subscriber of one of theV party line subscribers when the responds, mechanism is operated for prereceiver is oil the switch hook.` Inasmuch paring a charging circuit for charging a call as the'conduct'ors of a party yline might beagainst the calling subscriber upon his incomeaccidentally groundedby a permanent dividual message register as soon as the ground and thus would cause the operation conversation over the established connection of the discriminatory testingy means, regardis terminated, and the calling subscriber less of whether one or the other of two parties releases the connection by restoring his reon the line initiated the call, it isnecessary ceiver to its switchhoolr. j tovprovide means for dctectingthe imstandl/Vhen all subscribers lines terminating ard condition and for preventing-the,regisin an office of the exchange are individual trationot' the call uponeithery of lthe regislines, that is, are provided with but one ters of the substations of vthe line.l Itis 40 substation for each line, the registration of therefore an object of this invention to ,pro-

successful calls is a comparatively simple vide means for the selective registration matter, and in systems of the general charac'- of calls initiated upon party lines, upon 95 ter disclosed the registration may be effected message registers lindividual to lthe respecin substantially the manner disclosed in the tive substations on the line.v y A,

the patent to F. A. Stearn and F. J. Scud- A further object of the invention is the der, No. 1,395,977, issuedNovember 1, 1921.` provisionv of means for differentiating be- In the above mentioned patent a system is tween discriminatory testingjconditions es- 100 disclosed in which a group of subscribers7 tablished upon a calling line by the respeclines have access to a group of common distive substations thereon andan unstandard "O triot selectors through line switches indicondition of the line.

vidual to the subscribers lines. lilith each These objects are attained by` the` prolibi district selector is associates call charging vision Yof a special testing relay associated mechanism, which is operated upon the sucwith the district selector switch, which, durlli ing the establishment of a connection and prior to the response of the called subscriber, is first operated over a local circuit to ascertain if the relay is -in condition to function properly and is then connected to the t-ip conductor of the calling line. lf one subscriber has initiated the call the testing relay does not respond, but if the other subscriber initiated the call the relay responds and operates a switching relay at the district selector to switch the charging circuit from the :first subscribers register to the second subscribers register.

Upon the response of the called subscriber the call charging mechanism of the district selector is operated to further prepare the charging circuit for operating the selected subscribers message register upon the termination `of the conversation and the release of the connection. As soon as the callingsubscriber restores his receiver to the switch hook the release of the connection is initiated and the testing relay is again connected to the tip conductor of 'the calling line. If the line is in standard condition the testing relay does not function at this time and the call is charged. lf the line lis unstandard by reason of the connection of va Lit Lil)

stray ground to either conductor of the line, the testing relay operates at this time, prevents the charging of the call and causes the operation of a selector alarm device associated with the district selector.

The invention may be more readily understood by reference to the following description considered in connection with the accompanying drawings, in which Figure 1 shows one of a group of two party subscribers lines terminating in a full mechanical office of an exchange and a rotary line switch individual to such vline by means of which thefsubscribers line may be extended to an idle: district selector switch; Figures 2 and 3,' taken together, show the circuits 'of a district selector, a sender finder and so much of anoflice sender as is necessary for an nnderstanding of the invention; Figure L1 shows an incomingv selector switch provided with mechanism for applying ringing current to the terminals of a called line, together with the circuits and mechanism for controlling such switch; and Figure 5 shows the mechanism and circuits of a final selector switch and the line of a` subscriber to which the selector switch has access. The several figures of the drawing should be arranged, with Figurel at the left and the remaining ligures in consecutive order.

Description 07 apparatus.

The calling subscribers line is provided with two substations, each equipped with a transmitter, receiver and a ca ll bell, and since the lineterminates in a full mechanical cnice each substation is provided with an impulse dial. rEhe two substations differ from each other in that at one substation the call bell is connected from ground to the ring conductor of the line through a condenser when the receiver is on its switch hook, and from ground directly to the tip conductor when the receiver is olf the switch hook, whereas at the other substation the call bell is at all times connected from ground to the tip conductor of the line through a condenser. The substation of called line C, Figure 5, is of the usual type.

The calling line 'terminates in an individual line switch of the well-known step-bystep type, which, through a plurality of wipers, has access to a group of trunk lines terminating in district selector switches. The switch is provided with a stepping magnet for advancing the wipers over terminals of trunlr lines in search of an idle district selector switch and for advancing the wipers on around to normal position upon the release of the established connection. fissociated with each line switch are two message registers individual respectively to the substatious A and l and adapted to be operated over separate circuits extending through wipers of the line switch.

rlhe district selector, incoming seleetcr and final selector switches, shown in Figures I3, d and 5, are of the type shown and described in the patent to Craft and Rei'- uolds, 1,123,695, issued January 5, 1915. .Each of these switches has a vertically d posed switch shaft provided with tive seis of brushes, each brush set having access to a bank of one hundred terminals. For driving the switch shaft upwardly an updrivc magnet is proif'idcd, which, when energized, presses the switch shaft against a constantly driven power drum, for restoring the switch shaft to normal position a second downdrivc magnet, is provided, which, when energized, presses the switch shaft againr-:t a second constantly driven drum. For dctermining the particular set of brusln` cn the switch-shaft to be employed, a trippir spindle is provided asdescribed in the Patent 1,128,696 her-,inbefore referred to. The final selector switch differs from the other selector switches .in being provided with additional means comprising a second updrive magnet and driving` drum for driving the switch shaft upwardly at a higher speed than when driven by the first drum, where-- by the switch shaft may be advanced rapidly duriug its brush selection'aud group selection movements and more slowly during its terminal selection movement.

The sender finder switch SF and the steering switch shown at RS in Figure 2 are of the well-known step-by-step type, the

wipers ef which are advanced by stepping magnets. rlhe switch RS functions during a complete half revolution and upon the ital termination oi a connection is left with its wipers in normal position in condition for serving on a new call. The wipers ot nder switch SF have `no normal position, the

I wipers resting in contact with the bank terminals last employed by the switch when the switch is not being employed.

The otlice sender has been only partially disclosed in the dotted rectangle shown in the lower left-hand corner of Figure 2, only such portions of the sender being disclosed as are considered necessary 'for an understanding of this invention. The circuits ot a complete office sender are disclosed in the aforementioned patent to F. A. Stearn and l?. J. Scudder, 1,895,977. i

F or controlling `the circuits associated with the several selector switches and the circuits ot the otlice sender, auxiliary switches are provided. These switches may be of the type described in the patent to Reynolds et al, No. 1,127,808, issued. `February 9, 1915, and known in the art'as sequence switches. Each sequence switch comprises a rotatable shaft driven Yfrom a constantly operating source ot power through a magnetic clutch memberI and carries a plurality of circuit closing cams, which, at different radial positions ot the shaft, cause the closure of a plurality of contacts. rllhe cam contacts associated with each sequence switch are closed only in the positions indicated by the numerals associated therewith, with the exception ot' the master contacts 251, 301, 401 and 501, associated respectivelywith the switches 250, 800, 100 and 500, theselatter contacts being opened in the positions indicated by the numerals appearing adjacent such contacts and closed in all other positions.

The different pieces ot' apparatus vern- `ployed in the system having now been briefly described, it is thought that a clearer understanding` of the invention may be had Jfrom a description of the method of establishing a call. It will lirst be assumed that the subscriber at substation A desires a connection with the line of the subscriber at substation C, and that the directory number of the desired subscriber' is LISpenard 9532.

Detailed ope/ation 0 f cz'f'fcufts-Im'tz'atz'on of e @all 6,1/ party A.

The calling subscriber upon initiating a call establishes a circuit for the line relay 101 of the trunk hunting switch 100, which circuit may be traced from grounded battery through the right-hand winding' of relay 101, the innermost lower armature and back contact oit cut-ctin relay 102, over line conductor 108, through the subscribers loop at substation A, and thence back over line conductor 104 to ground at the upper armature and back contact ot relay 102. Line relay- 101 energizes in this circuit and closes a circuit for the stepping magnet 105 of the switch 100, which circuit may be traced from grounded battery through the winding and armature contacts of magnet 105, conductor 106, the lowermost armature and back contact of relay 102, the right-hand armature andA front contact of relay 101, conductor 107 and. thence to ground tlnough the wiper 108 and the normal contact of the bank to which-this wiper has access. The magnet, upon energizing, opens its own circuit and thereupon deenergizes advancing the wipers 108 to 118 inclusive of switch 100 to the second contacts of the respective banks to which they have access. As the second contact which wiper 108 engages is also permanently connected to ground, magnet 105 again 4energizes and advances the wipers to the third set of contacts leading to the first of thegroup of trunks to which` the switch has access. n i

it the first trunk of the group is busy there will be a ground potential VVon the test terminal thereotl appearing in the lowermost bank of the switch and the magnet 105 will continue to advance the wipers of the switch until an idle trunk is found upon the test terminal of which battery potential appears. llilhen this battery potential is encountered by the wiper 108, a circuit is closed from battery through the lett-hand contacts ot se-vk quence switch cam 802 (1) oit the district selector switch to which the first idle trunk extends, through the outer left-hand arma` ture andback contact of sleeve relay 200, conductor 114, wiper 108, conductor 107, the leftyhand armature and front contact-*and lefthand winding of relay 101, conductor 115 and thence to ground throughkboth windings of cut-ofi7 relay 102. Relay 102 energizes in this circuit and relay 101 is maintained energized over this circuit, through its lett-hand winding, after its initial energizing circuit, through its right-hand winding, is opened at the contacts o' relay 102. The energization of relay 102 opens the circuit of the-'stepping magnet at itslowermost armature andback contact and at its upper armature and back contact, and at its upper armature and front contact and uppermost lower armature and front contact, this relay extends the lconductors 104 and 108 of the subscriber-s line to the wipers 118 and 111 of the switch 100 and thence to the conductors 116 and 117 leading to the selected district selector. Relay 102, at its intermediate lower armature and front contact, also closes a circuit extending from grounded .battery through the right-hand winding ot sleeve relay 200, conductor 201, the break contact of the left-hand armature of slow releasing relay 325, the lower righthand contact ot sequence switch" cani 803 (1 to 21/2), conductor 326, the break contacts of the left-hand armature of switching relay 202, sleeve conductor 118, wiper 109, winding of marginal message register 119, conductor 120, the intermediate lower armature and front contact ot cut-ott relay 102 and thence toi ground through the upper winding of the cut-oft' relay. The sleeve re lay 200 of the district selector energizes in this circuit but due to its marginal winding the message regista-1 l magnet 119 does not energize at this time.

For marking the calling line busy to all calls incoming thereto, battery potential is connected to trie multiples of test terminal 121 appearing` in the banks of all iinal selectors having access to this line. To accomplish this a'circuit is established as soon as the switch 100 leaves normal positioinextending from grounded battery through the righthand winding of relay 124;, thence to gro-und through wiper 112 and the ott normal segment 125. Relay 124, upon energizing, connects battery to the test terminal 121 over a circuit extending from grounded battery through theleft-hand non-inductive windinc of relav 124, the armature and front contact of relay 124 and thence to terminal 121 over conductor 126. The Contact between wiper 112 and segment 125 also prepares a circuit extending over conductor 127 to the back contact and right-hand armature of relay 101, preparatory to restoring the finder switch 100 to normal position upon the termination otthe connection.

AUpon the energization of sleeve relay 200, a circuit is established 'for the line relay 327 of thevdistrict selector switch 350, which circuit extends from grounded battery through the right-hand winding of this relay, the upper lett-hand contact of sequence switch cam 304 (1), conductor 328, the lower contacts of sequence switch cana 305, conductor 329 and thence to ground through the frontcontact and right-hand armature of sleeve relay 200. At its outer left-hand armature and trent contact relay 200 connects ground potential tothe test conductor 1141 ot' the selected trunk to mark the trunk busy to other line switches, and at the back contact of this armature disconnects the source ot battery potential, which, up to the time the selector switch was seized, marked the selector switch as idle. The disconnection otl battery potential from test conductor 1111 now opens the holding circuit of relay 101 of the subscribers line switch and this relay deenergizes, the cut-ott relay 102, however, being` maintained energized over the circuit previously traced extending through the right-hand winding of sleeve relay 200. The deenergization of relay 101 is without effect at this time.

i Relay 327, upon energizing, closes a cire cuit for driving sequence switch 300 out of its normal position and into position 2, this circuitv extending from grounded battery through the winding of the drivingmagnet of switch 300, conductor330, the upper lefthand contact ot sequence switch camBOG (1), the inner right-hand armature and front contact of relay- 327 and thence to ground through the right-hand contacts ot sequence switch cam 307. The sequence switch magnet energizesin .this circuit and under the rcontrol ,of master cam 801 drives the sequence switch into position 2, in which position a circuit is closed from grounded battery through the rleft-hand winding ot' relay 325, conductor 331, the lower lett-hand contact et sequence switch cani 308 (2 to 11) and thence to ground. Relay 325,11 on energizing, closes a holding circuit iiort ie sleeve relay 200, extending through ltheright-hand windingof relay 200, conductor 201, the make contacts of the `left-hand armature of relay 325 and thence to the conductor 326 over he upper right-hand contact of vsequence switch cam 303 (13%,` to'lG), this circuit being maintained through,V position 16 of' the sequence switch or until relay 325 becomes deenergized. Upon reaching position 2 the sequence switch establishes a new circuit for placing ground potential upon .test conductor 114-, extending from ground lthrough the upper lett-hand contact of sequence switch 'ani 308, conductor 332 and thence to conductor 114l as previously traced, whichcircuit is maintained through position 1911/4c ot the sequence switch.

A; soon as the sequence switch reaches position 1%, a circuit is closed tor the stepping inaOnet 203 oit the sender finder SF, extending from grounded battery through the interrupter contacts and winding or inagnet 203, conductor 204, the upper lett-.hand contact of sequence switch cam 309 (1% to 2), conductor 333 and thence 4to ground through the inner right-hand larmature and front contact oit relay 327 and the right-hand contacts ot sequence switch cam 307. A'circuit isalso closed at thistime through the winding of stepping magnet208, the winding of cut-in relay 205` and thence over conductor 206 to groun'd'at the lower righthand con tact of sequence switch cam 308 (2 Ato "11). Relay 205' does not energize `at this time, however, since its winding is shunted by ground at the armature and front contact of relay 327. As soon as sequence switch 300 lea-ves position 1, the initial energizing circuit of relay 327 is opened the upper lefthand contact of sequence switch cani 304, but this relay remains locked up over a circuit extending from grounded Vbattery through its left-hand winding, `its left-hand armature and front contact, the rupper letthand contact of sequence switch cam 310 (1 to 6), the lower right-hand contact `of sequence switch cam 311 (1 to 21/4), conductor 334, test wiper 207 ofthe sender inder SF, and'to ground at busy contacts of the bank I over which this wiper moves. If the wipers of switch SF are at the time standing upon contacts which are connected to circuits extending to an idle otce sender, relay 327 does not lock up and the circuit previously traced through stepping magnet 203 is immediately opened at the inner right-hand armature and front conta-ct of relay 327 to prevent the advance of the wipers of switch SF. So long, however, as the test wiper 207 of the switch SF encounters contacts upon which busy ground potential exists, the stepping magnet 203 will advance the wipers of the switch until an idle sender is found, when the wiper 207 will lind no ground on the contact corresponding to the idle sender and the line relay 327 will thereupon become deenergized. Relay 327, upon deenergizing, opens, at its inner right-hand armature and front contact, the circuit previously traced, extending through the winding of the stepping magnet 203 and closes, at its inner right-hand armature and back contact, a circuit for driving sequence switch 300 out of position 2 and into position 3. This circuit may be traced from grounded battery through the magnet winding of sequence switch 300, conductor 330, the upper righthand contact of sequence switchv cam306 (2) the inner right-hand armature and back contact of relay 327 and thence to ground through the right-hand contacts of sequence switch cam 307.

As soon as relay 327 deenergizes, the shunt around the winding of cut-in relay 205 is removed at the inner right-hand armature and front contact of relay 327, and relay' 205 thereupon energizes in series with stepping magnet 203. Since the winding of relay 205 is of comparatively high resistance` sufficient current does not :flow in this circuit.

to cause the energization of stepping magnet 203. Relay 205, upon energizing, closes a circuit extending from ground through its front contact and armature 208, over .wiper 207 and the contact upon which it is now resting, conductor 209 and thence to grounded battery through the right-hand winding of relay 210 associated with the selected otiice sender. Relay 210 energizes in this circuit and causes the advancement of the time measure switch, not shown, associated with the. oiiice Sender in the manner fully set forth in the vpatent to Stearn andv Scudder, hereinbefore referred to, which.

from off normal contact 211, through thel left-hand winding of differential relay 210 and thence over conductor 209, whereby the sender is marked as busy until the oiiice vsender has been restored to normal condidesignation of the desired line.

"with the district selector.

tion, either followinggthe abandonmentof the call or upon the termination of the functioning ofthe ofiice sender. 4 i

With relays 210 and 205 energized,l an impulsing circuit is now established from the conductors of the calling line through the winding of the otlice register stepping relay 212 for enabling the calling subscriber to set the registers, not shown, associated with the otlice sender in accordance with the This. circuit 'may be traced from grounded battery through the armature and front contact of relay 210, conductor 213, wiper' 214, the in* ner right-hand armature and front contact of relay 205, conductor 215, the upper contact of sequence switch cam 313 (2S/LA to 10), trunk conductor 117, wiper 111 of the trunk finder switch 100, ythe innermost lower armature and front contact of relay 102, line .conductor 103, the impulse Acontacts 130 of the subscribers calling dial S,`thence through the subscribers substation circuits, line con- :ductor 104, the upper armature and front through the winding of stepping relay 212.

The calling subscriber nowy receives a dialing Atone over this circuit in the manner p set forth in the aforesaid Patent 1,395,977, and then proceeds vto dial the number of the desired line. Under the assumption that the subscriber desires a connection with a subscribers line C, which line is listed in the directory as LISpenard 9532, the subscriber proceeds to dial the three letters L I S corresponding to the'district designation of the district inv which the desired line is located, and-.then dials the four digits representing the number of the line in such district, which number, as assumed, is 9532. `The three letters which represent the district code will cause the setting of code registers (not shown) associated with the oiiice sender, which, in turn, control the operation of thev sender. to control the setting of the district selector switch 350 and the setting of the sequence switch of the district selector for determining the proper talking path through the repeating coil 336 rassociated y The transmission ofthe impulses corresponding to the number of the desired subscribers line`9532, causes the setting of the numerical registers `associated with the sender to control the sender to govern the setting of the incoming selector switch 150 and of the final selector switch .550, for extending the connection to the` desired line in the selected district. i

. Following'the setting of the code registers of the sender, the sequence switch 250, associated with the otce sender, is driven into positionv 2, in thek manner set forth in the be traced from grounded battery through the'let-hand winding of relay 327, the upper right-hand and lower left-handv .contacts of sequence switch cani 310, conductor 337, armature 2l7vaiid tront'contact of relay 205, wiper' 218, sequence switchicontact Y 219 i (2), the.. arinature and vback contact` of the 0 counting relay"220,'the` windings .ot polarized overflow relay 222, the windings of sender .stepping relay 221 and thence to` ground through the upper lett-hand and lower right-hand contactsof sequence switch cam` 223 andresistance element 224.

District brush and groupsclectz'om-f-.

Relay 827 of' the district selector switchl and stepping relay 221 ofthe ofice sender are energized in this circuit. Relay 221, upon energizing, establishes a circuit in the well-known manner for a counting relay of the code registers, and relay 32 7-closes a circuit for driving -sequence switch 3000i the district selector out of position 3 and into position 4. This circuit extends from grounded.battery through the magnet winding of sequence switch 300, conductor 330, the upper left-hand contact ot 'sequence switch cain 306 (3), conductor 333, the inner right-hand .armature andA front contact ofrelay 327 and thence to ground throughthe right-hand contacts of sequence switch cani 307. With the district selector sequence switch 300 `in position 4, the initialenergiziiig circuit of relayI 327- is opened at the" upper right-hand contact of sequence switch cam 310, but relay 827 is maintained' energized over the fundamental circuit by a new circuit extending from grounded bat tery through its left-hand winding, its letthand armature and rontcontact and thence through the upper lett-hand contactoflsequenceA switchI cani 310 (1 to 6) ,and over the fundamental circuit as which circuit extendstrom groundedfb'attery through the windingjot inagiiiett '338,

the-upper riglit-haiidco'ntact of sequencelswitch" cain 309 (4)', conductor. B33? and.

thence 'Ato ground through the; inner rights 'and front contact ot' relay previously` traced.. A circuitrisciiow closedffor thepupf. drive magnet 338 of the district selector,

V'tatiiig updrive drum 340, thereby causing the upward movement of the' switch shaft.

lAs the switch shaft otjtlie district selector switch moves upwardly and approaches its lrst brush tripping position,brush 341 engages the .tirst metallic portion ot the con'iinutator segment 342, and a circuit is closed as follows in shunt ot' the vindirrejs of the sender stepping relay 221, which may be traced from grounded battery through the lett-hand winding, left-hand armature 32T, the upper left-'hand' contact oi sequence switch cani 310 (1 to 6), the upper righthand contact ot sequence switch cani 811 to A4), con ductor 343",`coinniutator segment 342. brush 341, conductor 344 and thence to ground through the upper right-hand contact oi sequence switch cani `314 (9 to Y). Relay 327`is maintained energized over this shunt circuit, but relay 221, being shunted, dceiiergizes, causing, in the well-known ner, the energization of the. counting which is paired with the previously gized counting` relay.

As'tlie switch shatt continues in its upward movement, brush 341 moves into engagement with an insulating portion or' thc of the group of counting relays associatedl withthe sender corresponding to the setting.

segment 842 and the shunt around the windings of sender stepping relay 221 is removed, whereupon the sender stepping1 relay again energizes. In this inai'iner, during the upward movement o1 the switch shalit'oii the district selector. the stepping relay 221 ot' the office sender is intermittently energized and deenergi'zed. causing the successive energization oi" the count' relays associated with the sender. lt it be assumed that the No. 2 counting rela): was energized upoirthe initial energization ot' sender stepping relay 221, then.y when the switch shat't of the district selector has afivanced to such a position as to position the third set oi brushes carried thereby in posr tion to be tripped, the' No. O counting` relay 220 will be' energized in series with 'the No O counting relay 225 and will open the previously traced fundamental circuitat its armature and back contact. Counting relay 220 is also instrumental at this time in causing the advancement ot the sender sefpicnre switchr 250 out of position and into posiH tion 4 Upon leaving Aposition 2, all counting relays., which have been energized loclredV up over the circuit extending throu sequence switch coiitact226, beconie deenergized.

As soon `following the opening ottlie 'fuir dainental circuit by the No. O countir relay 220 as the brush 341 engages the ne insulating portion of coinn'iutator segment, 342,A relay 327 becomes deenergized and closes a circuit for driving the district selector sequence switch 300 out of position -land into position 5, and opens the circuit Cil i again energize.

previously traced through the updrive magnet 338, thereby arresting the upward moyement oi" the switch shaft 339. The circuit for driving sequence switch 300 into position 5 may be traced from grounded battery through the magnet winding ot sequence switch 300, conductor 330, the upper righthand contact of sequence switch cam 306 (4), the inner right-hand armature and bach contact ot relay 327 and thence to ground through the right-hand contacts of sequence switch cam 307. )Vith sequence switch 300 of the district selector in position and the sender sequence switch 250 in position 4, the fundamental circuit previously tract-d is again established and relays and i Relay 221 now establishes a circuit through one of the counting relays in accordance with the setting ot the code registers, and relay 327 establishes a circuit for driving sequence switch 300 out et position 5y and into position 6, this circuit eX- tending from grounded battery through the Amagnet winding of sequence switch 300. conductor 330, the upper lett-hand contact ot sequence switch cam 306 (5), conductor 333 and thence to ground through the inner right-hand armature and front Contact ot relay 327 and the right-hand contacts ot sequence switch cam 307. Upon leaving` position 5 sequence switch 300 opens the initi energizingcircuit of relay 327, but relay 327 is now maintained energized over the tundamental circuit through the upper 'letthand contact ot sequencev switch cam 310 (l to 6), and the left-hand armature and front contact and left-hand winding oi" renay 327.

Upon reaching position 6, the circuit previously traced through the winding ot updrive magnet is again established through the upper' right-hand contact of sequence switch cam 309 (6), auf in the manner previously described the switch shaft 339 is again driven upwardly.A Since at this time, however, the tripping spindle initial upward movement ot the switch shaft 339, and during the continued upward movement of the switch shaft the 4tripped set oit Abrushes travel over the contacts of the bant;

with which they are associated, Theremaining four sets ot brushes on the switchl shaft are not tripped at this time and therefore are functionless.

As the switch shaft continuesits upward movement and the tripped set of brushes .ap-

proaches the first st of terminals in the 221, which shunt circuit may be traced from grounded battery through the lett-hand winding, lett-hand armature and front contact of relay 327, the upper left-hand and,y

lower right-hand contacts of sequence switchl cam 310, conductor 349,l segment 348, brush 347, conductor 344 and thence to ground at the upper right-hand contact of sequence switch cam 314 (9 to 7). energized over this circuit, but ysender stepf ping relay 221 deenergizes, causing, upon its deenergization, the energization of a counting relay paired with the' counting relay which was energized upony the initial ener-y gization of relay 221. i

As the brush shaft continues in its upward movement, brush 347 engages an insulating portion of segment 348, and the shunt around the windings of sender stepping relay 221 is opened, whereupon relay 221 re-` energizes, caus'ng the energization of the next succeeding counting relay. In this manner, during the continued advancement ot the switch shaft the stepping relay 221, ot the sender is intermittently energized'and deenergized to energize and lock up suc-. cessive counting relays. It it be assumed that the subscriber has set the code registers in such a. manner as to cause the No. O counting relay 225 to become energized upon the initial energization oitl relay 221, then upon the Erst deenergization 'ot relay 221 the No. 0 counting relay 220 will become energized in series with relay 225,y thereby yopening the fundamental circuit and caus-` As soon following the opening ot the tundamental circuitby the No. 0 counting relay 220 as the brush A347 engages the next insulating portion of commutator 348, relay 327 becomes deenergized, opening at the front contact of its inner right-hand armature, the previously traced circuit of the updrive magnet 338 to arrest 'the upward movement of the switch shaft, and closing atthe back contact of its inner right-hand armature the prevfouslyvtraced circuit for ad'- vancing sequence switch 300 out of position 6 and into position 7.

At` the time 'sequence switch 300 moved into position 6, immediately prior to the Relay 327 is held .llO

group selection movement of the selector switch, a circuit was established for advancing the steering switch RS, Fig. 2, out ot its normal position 1 and into position 2. rlhis circuit may be tracel from grounded battery through he armature contact and winding ot stepping magnet 230, wiper 231, normal contact 232, conductor 233, conductor 23stand thence to ground through the lower lett-hand contact ot sequence switch cam 314 (6 to 7%). Stepping magnet 230 energizes in this circuit, battery being maintained connected to its winding over contact 227, wiper 223 and conductor 229, and is held energized until sequence switch 300 leaves position 7% when magnet 230 deenergizes to advance the wipers ot switch RS to the second position contacts.

With sequence switch 300 in position 7, a circuit is established for relay 327, whch may be traced through its right-hand winding, the upper lett-hand contact ot sequence switch cam 304 (7 to 71g), conductor 323, the lower contacts of sequence switch cam 305, conductor 329 and thence to ground through the right-hand armature and trout contact of sleeve relay 200. Relay 327, upon energizing, closes a circuit tor driving seque-nce switch 300 out ot position 7 and into position 3. rlhis circuit may be traced trom grounded battery through the magnet winding of the sequence switch, conductor 330, the upper lett-hand contact ot sequence switch cam 306 (7), the inner righthand armature and front contact ot relay 327, the upper left-hand contact of sequence switch cam .307 (7 to 3) and thence to ground through the make contacts of the right-hand armature ot relay 325.

As soon `as sequence switch 300 leaves position 7%, the initial energizing circuit or" relay 327 is opened at sequence switch cam 304, but it the first trunk in the group of trunks upon which the brushes 351, 352 and are now standing is busy, a. ground potential exists on the test Vterminal 354 and relay 327 is maintained energized over the circuit extending from grounded battery through its lett-hand winding, lett-hand armature and front contact, the lower letthand contact ot sequence switch cam 315 (715/2 to 9), the outer right-hand armature andY front contact of relay 327, the lower contacts `of sequence switch cam (7 to 3), brush 353 and terminal 354s, and when sequencekswitch 300 reaches position 3 a circuit isestablished for the updrive magnet 333. The circuit of updrive magnet 333 may be traced trom-grounded battery through the winding of this magnet, the upper righthand Contact of sequence switch cam 309 (3) the inner right-hand armature and front contact of relay 327 and thence to ground through the right-hand contacts ot cam 307. The updrive magnet 333, upon energizing,

drives the switch shaft upwardly in search ot an idle trunk in the selected group. 3o long as the test brush 353 encounters the tern'iinals ot busy trunks, relay 327 re mains locked up. vWhen, however, an idle trunk is encountered, which, it will be as shined, is the trunk terminating in termin: 355, 356, and 357, the locking circuit ot' rclay 327 is opened no ground potential exists on the test terminal 357 and relay 327 deenergizes as soon as the brushes have been properly centered on the banlr terminals 356 and 357. Until 'the brushes are so centered, relay 327 is maintained locked up over a circuit extending through righthand winding, the upper right-hand contact' ot sequence switch cam 305'; conductor 353, centering segment brush 360, con ductor 344e, the lower right-hand contact ot sequence switch cam 309 (3), conductor 333, the inner right-hand armature and Ytrout Contact oit' relay 327 and thence to ground through the right-hand contacts ot sequence switch cam 307. Relay 327, upon deenergizing, opens the previously traced circuit of the updrive magnet 333, thereby arresting the brushes 351, 3E 2 and 353 upon the terminals 355, 356 and 357 ot the trunk line extending to the district ot the exchange in which the desired line terminates. Relay 327 also establishes the previously traced circuit 'for c riving the sequence switch 300 out oit position 3 and into position 9.

As soon as sequence switch 300 reaches position 31/2, a busj7 ground potential is placed on the `multiples ot test terminal over a circuit which may be traced troni ground through the upper le't'tdiand coutact of sequence switch cani 315 (3l/; to 1111/2), the upper right-hand contact ot quence switch cam 315 (7 to 16), conductoi` 361, overflow segment 362, brush 363, con-- ductor 364, brush 353 and thence to the multiples ot terminal 357.

Relay 327 again encrgizes when sequence switch 300 reaches position 9 over a circuit extending through its right-hand winding, the upper lett-hand contact ot sequence switch cam 304; (9 to 10), conductor the right-hand contacts ot sequence switch cam v305 and thence to ground at the inner `left-hand armature and front contact ot message charging relay 365. Eelay was energized as soon as sequence switch 300 reached position el over a circuit extending trom grounded battery through its winding, the upper rightdiand contact ot sequence switch cam 316 (et to l0), conductor 366, the outer right-hand armature and trent Contact ot relay 205. conductor the upper lett-hand contact of sequence switch cam 317 (3 to 10), conductor 367, wiper 236 and thence to ground through the bacs: contact and armature ot advance relay 237 and resistance element 233. Relay 327, upon enlill) ergizing in the circuit previously traced, closes a clrcult through its right-hand arnature and front contact for driving sequence switch 300 lout of position 9 and into posi-v tion 10, in which position a` fundamental circuit is extended from the oilice sender through contacts of sequence switch cams 313 and 319 of the district selector to the line relay 421 of the incoming selector switch 450.

Incoming brush 0r thousands selection.

The fundamental circuit may now be traced from grounded battery through the right-hand winding of relay 421, conductor 422, the upper ri ght-hand contact ofsequence switch cani 402 (1 to 10), the upper left- -hand contact of sequence switch cam 402 (1),

239 of the sende-r finder switch SF, conduc` tor 240, conductor 369, the right-hand contacts of sequence switch cam 319, brush 352 and bank terminal 356 of the district selector switch, trunk conductor 420, Athe -lower contact of sequence switch cam 404 (1 to 10), resistance clement 425, conductor 426 and thence to ground at the lower contact of sequence switch cam 405 (1 to 8). The sender stepping relay 221 and the line relay` 421 of theincoining selector switch 450 energize in this circuit. Relay 221, upon energizing, establishes a circuitin the well-known manner for a counting relay corresponding to the setting of the thousands register of the sender, which in the case assumed is the'No. 4 counting relay. Relay 421, uponenergizing, closes a circuit for driving sequence switch 400 out of its normal position 1 and into position 2, this circuit extending from grounded battery through the winding -of sequence switch magnet 400, the lower righthand contact of sequence switch cam 406 ((1) the outer left-hand armature vand front contact of relay 421, conductor 427 and thence to ground at the lower contact of sequence switch cam 407 (1 to 10). As soon as sequence switch 400 leaves position 1, lthe initial energizing circuit of relay 421 is opened at the upper left-hand contact of sequence switch cam 402butl relay 421 remains energized over the fundamental circuitthrough a locking branch of the vfundamental circuit which may be traced from grounded battery through the right-hand vlwinding of relay 421, the right-hand contact-s of sequence `switch cam 402, conductor 428, the righthand armature and front contact Vof relay 421, conductor 429, the left-hand contacts of sequence switch cam 408 l(1 to 4) andthence over thefundaniental circuit as previously traced.

With sequence switch 400 in position 2 a circuit is closed for the updrive magnet ,430', vwhich may be traced from grounded battery through the winding of this magnet, the upper right-hand contact of sequenceswitch cam 409 (2), conductor 43,1, theout'er lefthand armature and front ,contact of relay` 421 and thence to ground at the lower contact of sequence switch cam 407 y(1 to 10). Magnet 430, upon energizing,v pressesthe depending portionl of the switch shaft 432 f against the constantly rotating f updrive `drum 433, causing thereby the upward move--r ment of the switch shaft. During the upward movement of the switch Vshaftfand as 'the shaft approaches its iirstbrush trippingposition, brush 436 engages theJ metallic por. 'i

tion of segment 434 of thecommutator 435 and a circuit is closed inshunt of thel windings of sender stepping relay 221, which circuit lmay be traced from grounded battery through the right-hand winding of relay 421, the right-hand contacts of sequence switch cam 402, conductor 428, the righthand armature and front contact of-relay 421, conductor 429, thev upper left-hand andl lower right-hand contacts of sequence switchcam 408, segment 434,(bru'sh 436, conductor 437 and thence to ground at thelower right-hand contact of sequence switch cam 410 (7 to 5). Relay 421 is maintained over this y shunt circuit but relay 221y is shunted down and'deenergizes. v, Y.

Relay 221, upon deenergizing, causes the energization of the No.4" counting relay in the well-known manner. As the `switch shaft 432 of the incoming selector switch continues in its upward movement, the brush 436 engages an insulatingv portion of the commutator segment 434, whereby the previously traced shunt circuit is opened and relay 221 upward movement, or until the No 0 counting relay 220becomes energized, when'the previously4` traced fundamental rcircuit` ,1s

lopened at-'the armaturelcontacts Aof relay 220 and the sequence switch 250 of the oiiice sender is advanced out'of position` 6 andinto position 8f When sequence switch-250 leaves position 6 the circuit-over which-the vener.-

gized counting relays lia-ve been ,locked up is` opened at sequence switch cam 226.

As soon following the opening of the` fundamental cir'cuitbyi the No. l0 counting re` lay 220 as the brush 436 engages the next insulating seginentlof the commutator 434, relay 421 becomes kdeenergized.

position asv to 'condition vthe fifth set of brushes thereon to 4be tripped upon the subsequent upward movement of theV switch shaft. ARelay 421, upon deenergivzing, opens thev previously traced circuit extending 4through the winding of the updrive magnet 430 for arresting the Aupward movement of the switch shaft and closes at its inner left-hand armature and hack contact a cir- ,cuit

cuit for driving the sequence switch 400 out of yposition 2 vand into lposition 3, this v.cir-

eXtending from grounded battery through the winding fof the driving magnet Aof the sequence switch, the upper left-hand thence tomground Athrrnigh the" right-hand lcontacts of sequence switch cam 405.` Trip `magnet 488, Aupon energizing, rotates the tripping spindle 439V into such a position as will trip the selected set of brushes upon the subsequent upward movement olf ythe vswitch shaft 432.

Incoming gro-up selecz'on.

With sequence switch 400 in position o and the sequence switch 250Y of .the office sender in vposition 8, the Vpreviously traced fundamental circuit is again closed. The sender stepping "relay 221 and linerelay L421 of the incoming` selector switch venergize in this circuit, relay 221closing'a circuitffor'a lower counting relay ofthe ygroup of counting relays associated with the sender, which, in 1this case, lwill be assumed to be the No. 2 counting relay.v Relay 42,1, upon energizing, again closesthe circuit previously traced'pfor driving the sequence switch l400 out Iof position 3 andinto position 4, andiat its right hand armature and front contact closes the previously traced locking circuit for maintaining itself energized over the `fundamental circuit yafter sequence switch400 leaves position. With sequence switch 400 inpesition 4 and relay 421 energized; the circuit previously traced through the l,updrive magnet 430 4is again closed and the switch shaft v43,2 is drivenupwardly in its group selection movement.

' During the initial upward travel ofthe l:switch shaft the fifth s eto'f .brushes "is tripped by :the tripping lspindle 439`,"and

,during the sulfiseq'uent upward moveiiientof uit' Switch ,Shaft uit tripped .Safer ,brushes travel infengagementwith the .'terininalsof te@ .bank .with vhb they all? repeatedy The switch kshaft 432 has now been moved into suoli a The remaining four sets of brushes not haring been tripped are functionless. As the tripped set of brushes on the shaft of the` lswitchapproaches the lower-most set of terminals inthe first subgroup of terminals of its bank, the brush 441 engages the metallic portion ofthe commutator segment 440 and acircuit isclosed in shunt ofthe winding of thelsender stepping relay 221, which may be traced as follows: from grounded batter)v through .the right-hand winding of relay 421, conductor 422, the right-hand contacts yof sequence switch cam 402, conductor 428, theright-hand armature and front Contact of relay421, the upper contacts of sequence .switch cam 408, commutator segment 440, vbrush 441, conductor 437 and thence to ground ,at the lower contact of sequence switchcam 4,10 (7 to 5). Relay 421 is maintained energized over this shunt circuit but the sender stepping relay is shunted dowi. y.and deenergizes. i

Upon the Vdeenergization of sender stepping relay 22l,`the No. 2 counting relay he "comesenergized in the well-known manner. As the switch shaft 432 continues in its upward movement, the brush 441 engages an insulating portion of segment 440 and the previously traced shunt circuit is opened, whereupon the sender stepping relay 221 again energizes. 1n this manner the sender stepping relay is intermittently energized and deenergized as the switch shaft 432 continues inits upward movement, until the No. 0"'counting relay A220 becomes energized, when the fundamental circuit is opened :u its armature contacts and `the sender sequence switch 250 is advanced. out ot' posi-l tion 8 and into position 10. Sequence swieh 250upon leaving position 8, opens the lochingcircuit overwhlich the energized count-- ing'relays are maintained energized at quence switch cam 226.

As soon vfollowing' the opening of the fundamental circuit by the No. O counting relay 220 as therbrush 441 engages the next insulating portion vof lcommutator segment 440, relay 421 deenergizesuopening the circuit previously traced through the winding of the updrive magnet 430, thereby arresting the upward movement of the `switch shaft. At Aits inner left-hand armature and been Contact, relay 421 closes the circuit previously traced for driving the sequence switch 400 out of position 4.and into position 5. In position ,5 relay 421 is again energized over a circuit extending from ground edhattery through its left-hand winding, andthence to ground .through the right-hand ieontalctsfof sequence switch cam411. Relay 42`1w`iioiv clos'esfa circuit extending from ,ground atseeluencel switch "ca1n"'407, Vand throiigh Vtheouter' left-'hand armature and Vfront contact' ofrelay 1421 for driving sei,duendeswitch 400 out of position andinto position 6. Upon leaving position 5% the initial energizing circuit extending through the winding of relay 421 is' opened at se?v quence switch cam 411, but relay 421 remains energized over a' locking circuit extending from grounded battery through its right-hand winding, the right-hand contacts of sequence switch cam 402,conductor. 42h, the right-hand armature and front contact 0f relay 421, conductor 429, the right-hand contacts of sequence switch cam 412, and thence through test brush 442 to ground on the test terminal 470 of the first trunk lof the group to which the brush set has been moved during the group selection movement of the switch shaft, provided the first trunk of the group is at the time busy.

`When sequence switch 400 reaches position 6, if relay 421 is at the time locked up, al circuit is closed as previously traced for energizing the updrive magnet 430 for driving the switch shaft 432 upwardly in its trunk hunting movement. This movement will continue so long as the test brush 442 encounters ground potential on the test terminals of trunks of the group over which this brush moves. When, however, anidle trunk is found, which, it will be assumed, is the trunk terminating in terminals 447 449 and 451, the locking circuit of relay 421 will be opened since no ground potential exists on the test terminal v451. Relay 421 thereupon deenergizes, opening, at its outer left-hand armature and front contact, the circuit of the updrive magnet 430. To insure. however, that the brushes shall be properly cenv tered on the terminals of the selected idle trunk, relay 421 is locked energized to maintain the circuit of the updrive magnet 430, until the brushes are properly centered, by an additional locking' circuit extending from grounded battery through the left-hand winding of relay 421, the upper right-hand and lower left-hand contacts of sequence switch cam 411, conductor 443, the centering commutator segment 444, brush 445, conducto-r 437, the upper left-hand contact of sequence switch cam 410 (6), conductor 431,

and thence to ground through the outer left-hand armature and front contact of relay 421 and the lower contact of sequence switch cam 407.

Upon the deenergization of relay 421, following the centering of the brushes of the switch upon the terminals of the selected idle trunk, the circuit previously Vtraced is closed for driving sequence switch 400 out of position 6 and into position 7. In position 7 relay 421 again energizes in a circuit extending through its left-hand winding and the righthand contacts of sequence switch cam 411, and again closes the previously traced circuit for driving sequence switch 400v out of position 7 and into position 8, in which position the tip conductor of the incoming trunk cir- '221 and relay 518 of the final selector become energized. Sender stepping relay 221. upon cuit are extended through a contact ofps'equence switch cams 413. The fundamental circuit is now extended to the final selector switch 550 and may be traced from grounded battery through the upper left-hand contact of sequence switch cam 504 (1l to 10), the right-hand winding of relay 518, the lower left-hand contact of vsequence switch cam 503 (1), the lower left-hand contact o-f sequence switch cam 502 (15 to 6), trunlcon-` ductor 517, bank terminal 447 and brush 446 of the incoming selector switch 450, 'the upper left-hand contact of sequence switch cam 413, resistance element 424, the upper contact of sequence switch cam 403 (1 to 10) thence, as previously traced, over the fundamental circuit through the winding ofsender stepping relay 221, and returning through the lower contact of sequence switchy cain404k1 (1 to 10), resistance element 425, conductor 85 426, and thence to ground at the lower contact of sequence switch cam 405 (1 to 8).

`Upon the extension of connection to the final selector switch, relay 421 of the incom-` ing selectorswitch, which' was energized in position 7 of sequence switch 400is maintained energized when the sequence switch reaches position 8 over a circuit extending from Igrounded battery through its righthandy winding, `conductor 422, right-,hand 95 contacts of. sequence switch cam 402. conductor 428, right-hand armature and front contact of rclay421, lower right contact of sequence switch cam 414 (7 toS). brush 448 and terminal 449 of the incomii'ig selector switch, trunk conductor 519,;the upper lefthand and lower right-hand contacts of `sequence switch cani 505. resistance velement 520. and thence to ground through the lower left-hand Contact of sequence switch cam 506 (1 to 81/3) this circuit beingmaintained until the sequence switch 500 of the final` selector switch leaves position 8'1/2 following the units selection. Busy ground potential placed on the multiplesof testy terminal 451 of the selected trunk over' test brush 442`and the lower right-hand and upper left-hand confacts of sequence switch cam 412.

Fin .Z 4. 71. Pc cati '11',

(l )frs ,Z 0 115 Upon the extension of the abovelraced fundamental circuit to the inal selector switch 550 with the sender sequence switch 250 in position 10. the sender stepping relaja energizing, establishes a kcircuit for the No. 4 counting relay in the well-known manner, it being assumed that the calling subscriber has so set the thousands and lnuidredsregister' as to prepare the circuit of the 1ro. 4 counting relay. p

Relay 518, upon energizing, establishes a circuit for relay 521, which may be traced from grounded battery through the left-hand winding of this relay, conductor 522, the upof sequence switch cam 508 (1 to 11). Relay 521 energizes in this circuit and at its leftha-nd armature and front contact closes a locking circuit for itself extending from grounded battery through its left-hand winding, through the armature and back contact of test relay 524;, the left-hand armature and frontcontact of relay 521, sleeve conductor 525 of the trunk circuit extending to tlietinal selector switch 550, bank terminal 451 and brush 41412 of the incoming selector switch, and thence to ground at sequence switch cam L112. Relay 521, upon energizing, closes a circuit for driving sequence switch 500 out of its normal position into position y 2, which circuit may be traced from grounded lbattery through the winding of magnet 500,

through the lower contacts of sequence switch cam 509, and to ground at the right- Yhand armature and front contact of relay 521. `When sequence switch 500 moves out of position 1, the initial energizing circuit of relay 518 is opened at the lower left-hand contact of sequence switch cam 503, but relay 518 is maintained energized over the fundamental circuit by reason of a locking circuit extending from grounded battery through the upper left-hand contact of sequence switch cam 504:, the right-hand winding of relay 518, the lower right-hand contact of sequence switch cam 510 to 10) the righthand armature and front contact of relay 518, the lower right-hand contact of sequence switch cam 503 (1 to 6), and thence through the left-hand contact of sequence switch cam 502, and over the fundamental circuit as previously traced. Relay 518 also closes a'circuit as soon as sequence switch 500 reaches position 2, which may be traced from `grounded battery through the winding of the high speed updrive magnet 526, the upper righthand contact of sequenceswitch cam 511, (2) conductor 523, left-hand armature and front Contact of relay 518, and thence to ground at the upper left-hand contact of sequence switch cam 508. Magnet 526, upon energizing, presses the depending portion of the switch shaft 527 against the constantly rotating high speed drum 528, thereby causing the switch shaft to be moved upwardly at a high speed in its brush selection movement. During the upward movement of the switch shaft and as the brush shaft approaches its first hrush tripping position, brush 532 engages the metallic portion of the commutator segment 530 of the commutator 531 and a circuit is closed in shunt of the windings of the sender stepping relay 221, which may be traced from grounded battery through the upper left-hand contact of sequence switch cam i (1 to 10), the right-hand 'vindingl of relay 518, the lower contact of sequence switch cam 510 (15 to 10), the right-hand armature and front contact of relay 518, thix lower right-hand contact of sequence switch cam 503 (1 to 6), 'the unner right-hand contact of sequence switch cam 502 (1/iA to conductor 529, commutator segment 520, brush 532, conductor and thence to ground through the upper left-hand contact of sequence switch cam 506 (13 to 11). lieta)v 518 is maintained energized over this shunt circuit but sender stepping relay is shunted down and hecomes deeuergized.

Upon the first deenergization of sender step-ping relay 221, the counting rela)V paired with the counting relay, which was energized upon the initial energization of rela-y 221, in this case the No. 4t countingv relay becomes energized and locks up in the well-known manner, As the switch slnift` 527 of the final selector switch continues in its upward movement, hrush 582 engages an insulating portion of the commutator seifment 530, and the previously traced shunt circuit is opened, whereupon the sender stepping relay 221 again euergizes and cstablishes an energizing circuit for the next succeeding counting relay No. 3. In this manner, as the switch shaft continues in its upward movement, the sender stepping relay 221 intermittently energizes and decuergizes, thereby energizing the counting relays of the sender in succession untily the No. 0 counting relay 220 becomes energized, when the previously traced fundamental circuit is opened at the armature contacts of counting relay 220 and a circuit is estalilished for advancing the sender sequence switch 250 out of position 10 and into position 12. lVhen the sequence switch 25o leaves position 10, the circuit extending over the contact of cam 226. over which the energized counting relays were maintained locked up,- is opened and these relays deenergize.

As soon following the opening` of the fundamental circuit by the No. OYcountinfr relay 220 as the brush engages the next insulating portion of commutator segment 530, relay 518 becomes deenergized, opening` the previously traced circuit of the updrive magnet 526 and closing a circuit for advancing the sequence switch 500 out of position 2 and into position 3. The circuit of sequence switch 500 may be traced from grounded battery through the magnet winding of sequence switch 500, the upper righthand contact of sequence switch cani 512, the left-hand armature and back contact of relay 518, and thence to ground through the upper left-hand contactof sequence switch cam 508. The fifth set of brushes has now been posiover a circuit extending from grounded battery through the trip magnet 535, and thence to ground at the lower right-hand cont-act of sequence switch cam 506 (3 to 5), as soon as sequence switch 500 reaches position 3.

Fin-4Z group or tens selection.

When sequence switch 500 reaches position 3, the energizing circuit of relay 518 is again established over the fundamental cir-k cuit as previously described. andrelay 518 and stepping relay 221 of the office sender again energize. Sender stepping relay 221, upon energizing, establishes a circuit for the No. 3 counting relay, it being assumed that the calling subscriber has set the hundreds numerical register in such a position as to condition the circuit of the No. 3 counting relay for completion upon the initial energization of the sender stepping relay 221 during the group selection movement of the final selector switch.

Relay 518, upon energizing, again closes the previously traced circuit for driving the sequence switch 500 out of position 3 and into position 4. Vith sequence switch 500 in position l the previously traced circuit for the updrive magnet 526 is again established at the left-hand armature and front contact of relay 518. Relay 518 also establishes the previously traced locking circuit for itself extending through its right-hand armature and front contact for maintaining itself energized over the fundamental cir- 'cuit after sequence switch 500 leaves position 3 and opens the initial energizing circuit at the lower left-hand contact of'sequence switch cam 503 The high speed updrive magnet 526,'upon energizing, again drives the switch shaft 527upwardly in a. group selecting movement. During the initial portion of this movement the fifthv set of brushes is tripped by the tripping spindle 534; and during the remainder of the group selection movement the tripped set of brushes travel upwardly in contact with the terminals of the lbank with which the brush set is associated. The remaining Vsequence switch cam 506.

As the brush grounded battery through the left-hand contact ofsequence switch cam 504 (1 t`o'10) the l right-hand winding of relay 518, the lower right-hand contact of sequence switch cam 510 (15 to 10), the right-hand armature and front contact 'of relay 518, the righthand contacts of sequence switch cam 503, conductor 536, commutator segment 537, brush 538, conductor 533, and thence A.

to ground at the upper left-hand contact of Relay 51,8 is maintained energizedjin this shunt circuit but sender stepping 'relay 2211s' shunted down and deenergizes, whereupon a circuit is established in the well-known manner for the No. 3 countingrelay. Y

As the switch shaft 527 continues in'its` upward movement, the brush 538 engages an insulating portion of thecommutator segment 537 and the previously traced shunt circuit is opened, whereupon the sender step-` ping relay 221 again energizes andl now establishes in the well-known manner-a circuit for the No. 2 counting relay. In this manner, as the switch' shaft 527 continues in its upward movement, the sender stepping relay 221 is intermittently energized and deenergized, thereby energizing the counting relays of the sender in succession, until the y No. 0 counting relay 220 becomes energized, when the fundamental circuit is opened at the armature contacts of relay 220 and a circuit is established for driving the sender sequence switch 250 out of position 12 and int-o position 14. When Athe sender sequence switch leaves position 12 thej'circuit over which the energized counting relays are maintained locked up is opened at sequence switch cam 226. As soon following the-opening of the fundamental circuit by the No. 0 counting rey lay 220 as the brush 538 engages the next in-l sulating portion of commutator segment 537 the holding circuit of relay 518 is opened and relay 518 becomes deenergized. Relay 518, upon deenergizing, opens the circuitof the updrive magnet 526 and closesthe cirv cuit reviously traced for driving sequence y switc 500 out of position 4 and into posiltion 5. In position 5 the fundamental cir-L cuit eXtending through the winding of step- M ping relay 221 and the right-hand winding' of relay 518 lis again established and relay"l 518, upon energizing, closes the previously"j' traced locking circuit for itselfy and estab# lishes a circuit for driving sequence switch 500 out of position 5 and into position 6.

magnet v539, the lower left-hand contact of sequence switch cam 507v (6), conductor 523.

circuit is established for thelo'w speed upv lil) thel'et-,hanld armature and front contact of relay 518, and thence to ground at the upper left-hand contact of sequence switch cam 508,l The low speed updrive magnet 539, upon energizing, presses the depending portion oit the switch shaft 527 against the constantly rotating low speed drum 5110, thereby causing the upward movement of the switch shaft in its units selection movement.

As soon as the switch shaft 527 starts in itsupward movement the commutator brush 532 engages a conducting portion of commutator segment 580, whereupon a circuit is closed in shunt ot the windings of the sender stepping relay 221, which may be traced from grounded battery through the letthanldhcontact of sequence switch cam 504 (1 to 10), the right-hand winding of relay 518, the lower right-hand contact of sequence switch cam 510 (15 to 10), the right-hand armature and front contact of relay 518, the lower right-hand contact of sequence switch cai-n` 503 (1 to 6), the upper right-hand contact of sequence switch cam 502 (5% to 6), conductor 529, commutator segment i 530, brush 532, conductorv 538, and thence to ground through the upper lett-hand Contact of sequence switch cam 506 (1ito 11). Relay 518 is maintained energized in this circuit but sender stepping relay 221, being shunted down, deenergizes.

.The sender stepping relay 221 ot the oti'ice sender, upon' energizing in the fundamental circuit with the sender sequence switch in position 111, establishes a circuit for the No. 2 counting relay, it being assumed that the calling subscriber has set-the units register of the sender in a position to condition the No. 2 relay for operation. Upon the .tirst deenergizatio'n of relay 221, the circuit of the No. 2 counting relay is established in thewell-known manner. As the final selector` switch shaft continues in its upward movement, brush 582 engages an insulating portion of segment 530 and the previously traced shuntcircuit is opened, whereupon sender Stepping relay 221 again energizes, establishing, the well-known manner, the energizing" circuit of the No. 1 counting re lay. In this manner, as the switch shaft moves upwardly, the sender stepping relay 221 is intermittently energized and deenergized until Vthe No. 0 counting relay 220 be-y comes energized when the fundamental cirruit is opened at its armature and back contact and a circuit is closed for advancing sequence switch 250 out of position 14 and into position 16.

ris soon following the opening of the tundamental circuit by the No. 0 counting relay `as brush 532 engages the nent insulating portion of the commutator segment 580, relay 518 becomes deenergized, opening the previously traced circuit of the low speed updrive magnet 539, and closing the previously traced circuit for advancing sequence switch 500 out ot position 6 and into position 9.

The brushes of the final selector switch 550 have now been positioned upon the terminals ot the desired line and sequence switch 500, upon reaching position 8% closes a circuit tor reenergizing relay 518, which circuit may be traced trom grounded battery through the lett-hand contact ot sequence switch cani 5011 (1 to 10), the right hand winding or relay 518, the lower right hand and upper lett-hand contacts o1 sequence switch cam 510, and thence to ground at the righthand armature and front contact oit relay 521. Relay 518, upon energizing, closes a locking circuit for itself entending from grounded battery through its right-hand winding, the lower right-hand contact of sequence switch cam 510, the right-hand armature and trent contact oi' relay 518, and thence to ground through ythe upper contacts ot sequence switch cani 518. This locking circuit will be maintained through position 10 ot sequence switch 500. Relay 518, upon energizing, also closes a circuit as previously traced for driving sequence switch 500 out of position 9 and into position 12. When the sequence switch reaches position 10 a new holding circuit is established tor relay 518, extending troni grounded battery 'through the lett-hand winding of relay 518, the lower right-hand contact ot sequence switch cain 515, (10 to 11), the left-hand armature and trout contact ot relay 518, and thence to ground at the upper left-hand contact oit sequence" switch cam 508. Upon reaching position 1l sequence switch 500k establishes a new holding circuit for relay 518, extending 'from ground through the winding of test relay 5211, conductor 541, the upper lett-hand contact ot sequence switch cam 502 (11 to 18), the lower left-hand contact ot' sequence switch cani 503 (11 to 13), the rightdiand winding of relay 518, the upper right-hand contact ol" sequence switch. cam 510 (11 to 121/2), the right-hand armature andtront contact orn re lay 518, the right-hand contacts oit sequence switch cam 513, test brush 5412, and thence to battery on the test terminal ot the called line it the called line is busy. lt the called line is busy as a calling' line this battery potential will be connected to the test terminal 543, as previously described, in connection with the trunk hunting switch 100 through the trunk hunting switch, and if the called line is busy as a called line, battery potential will be supplied to the terminal 543 from grounded battery through the upper righthand contact ot sequence switch cam 504 of the final selector switch, which is in engagement with the multiple terminals or the called line, the lower contacts of the cam corresponding to cani 513 and the test brush of such linal selector switch.

n Testing the called Zine-Zine busy.

If the called line is busy, relay 518 remains energized when sequence switch 500 reaches position 12 and relay 524 also energizes in the locking circuit traced through the right-hand winding ofrelay 518. The energization of relay 524 opens the previously traced holding circuit of relay 521, which relay thereuponv deenergizes, closing a circuit extending from grounded battery through the magnet winding of sequence switch 500, the lower right-hand and upper left-hand contacts of sequence switch cani 509, and the right-hand armature and back contact of relay 521 for driving the sequence switch 500 out of position 12 and into position 13. l/Vhen sequence switch500 leaves position 121/2, the test circuit traced through the windings of relay 524 and 518 is opened7 but relay 518 remains locked up over a circuit extending through its left-hand winding, the lower right-hand contact of cani `515 (12% to 14), the left-hand armature and front contact of relay 518, and to ground at the upper Contact of sequence switch cani 508 (12% to 16). When sequence switch 500 reaches position 13, relay 521 is again energized over a circuit extending from grounded battery through its left-hand winding, conductor 522, and thence to ground through the upper right-hand contact of sequence switch cani 506 (13), and locks itself to conductor 525 through the back contact and armature of test relay 524which deenergized when sequence switch 500 left position 12%. Relay 521, upon reenergizing, closes a circuit fordriving sequence switch 500 out of position 13 and into position 14, this circuit extending from grounded battery through the magnet winding of sequence switch 500, the lower contacts of sequence switch cam 50,9, and thence to lground at the right-hand armature and front contact of relay 521,. )When sequence switch 500 reaches position 14, a circuit is established for the downdrive magnet 544, which may be traced from grounded battery through ythe magnet 544, the lower righthand contact of sequence switch cam 511 (14), conductor 523, the left-hand armature and front Contact of relay 518, and thence to ground through the upper left-hand con-.

tact of sequence switch cani 508.

Upon the energization of the downdrive magnet 544, the depending portion of the switch shaft 527 is pressed against the constantly rotating downdrive drinn 545, thereby causing the downward movement of switch shaft 527 into normal position.v

When the switch shaft reaches'norinal position a circuit is established for driving seposition 17.

from grounded battery througha the wind-4 Q ing of sequence switch magnet 500, the upper left-hand contact of sequence switch cam 512 `(3 to 16), conductor 546, normal segment 547 of connnutator 531, brush 538,

conductor 533, and thence to ground through the upper4 left-hand contact of sequence switch cam 506. Upon leaving position 14, the lockingcircuit of relay 518` is opened, but in position 17a circuit is closed extending from grounded battery through the lefthand winding of relay 518, and thence to ground through the upper left-hand contact of sequence switch cam 515'- (17) and through interrupter 548. Relay 518 is intermittently energized in this circuit and at itsk left-hand armature and front contact intermittently connects a source of busy tone current 549 to the ring conductor 519 of the trunk circuit over a circuit extending from` ground through the secondary winding of tone coil 549, the lower right-hand contact of sequence switch cam 508 v(17), the leftliand armature and front contact of relay 518, conductor 523, the upper left-hand contact of sequence switch .cani 511 (17),

resistance 520, and the lowerright-hand and i upper left-hand contacts of sequence switch cani 505. rlone currentis conducted over the trunk circuit extendingto the calling subscribers line since at this -tini'e the subscribers line has become disconnectedfroinv the oflice sender at cams 312 and 313 of the district selector switch, as will be presently described. The circuit of the final selector switch is maintained in this condition until the` calling subscriber releases the connection in response to the busy signalin a manner to be described hereinafter. i

Testing the 'called Zine-Zine idle.

is established to this idle line, the circuit,

previously traced through the right-hand winding of relay 518 and the winding of test rela-y 524V will extend from ground to ground, and relay 518 will therefore become deenergized when sequence switch 500 leaves position 11 and test` relay 524 willnot become energized. When therefore relay 518 deenergizes it closes'a circuit for driving sequence switch 500 out of position 12 and into position 13, this circuit extending from grounded battery through the upper right- 

